TEM CHARACTERIZATION OF DEFECTS IN LEC-GROWN GAAS SUBSTRATES

The defects in semi-insulating LEC grown GaAs, perfect dislocations and polycrystalline As precipitates, are investigated by transmission electron microscopy. Vacancy type perfect dislocation loops are found to transform into incomplete stacking fault tetrahedra. In spite of the observation of arsenic precipitates, climb because of supersaturation of vacancies is found to be important for the formation of the observed dislocation configuration. This is discussed using a model of temporal succession of precipitation and dislocation climb. The most likely climb mechanism is that Ga vacancies are the driving force for a climb process during which As antisites are created.